1. Field of Invention
This invention relates to an optical pickup device. More particularly, it relates to an optical pickup device equipped with a metallic cover for covering wires of a laser diode.
2. Prior Art
An optical disk device is provided with an optical pickup device to write information on an optical disk and read information therefrom by a laser diode. The laser diode may be very hot under some operating conditions. If the laser diode is used long time at a high operating temperature, its efficiency, service life, and reliability go down. To prevent this, the optical pickup device must be designed to be high heat radiation performance so that the laser diode may always work below its assured maximum operating temperature.
Particularly in recent years, optical disk devices have been demanded to shorten time to record and reproduce information. This makes the laser diodes have higher outputs and become much hotter. Therefore, it is very important to increase the heat radiation performance of the laser diode.
The temperature of the laser diode in the optical pickup device can be reduced by increasing the quantity of heat release from the laser diode, that is, by reducing the heat resistance of a heat-radiating route from the laser diode to a housing or providing a heat-radiating route from the laser diode to non-housing parts.
Japanese Patent Application Laid-Open Publication No. Hei 10-83564 (Patent Document 1) discloses a method of caulking a lead-frame type laser diode to the metallic housing. This method can reduce the heat resistance between a laser diode and a metallic housing and increase the characteristics of the heat radiation performance to release heat from the metallic housing without aged deterioration change in connection of the laser diode and the metallic housing.
Japanese Patent Application Laid-Open Publication No. 2000-251297 (Patent Document 2) discloses an optical pickup device comprising a laser diode equipped with a common terminal, a printed circuit board connected to the laser diode, and a shield casing to cover the printed circuit board and the bottom of the laser diode, wherein the common terminal is soldered to the shield casing to transfer heat from the laser diode to the shield casing.
Japanese Patent Application Laid-Open Publication No. 2005-235288 (Patent Document 3) discloses an optical pickup device wherein a laser diode is supported by a first supporting member with large thermal conductivity, the first supporting member is soldered to a second supporting member with smaller thermal conductivity than that of the first supporting member and supported by a carriage, and the first supporting member is connected to the carriage through a thermal conductive material with high thermal conductivity, so that heat generated in the laser diode is efficiently transferred to the first supporting member and then to a place far from the laser diode through said thermal conductive material.
Patent Document 1: Japanese Patent Application Laid-Open Publication No. Hei 10-83564
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2000-251297
Patent Document 3: Japanese Patent Application Laid-Open Publication No. 2005-235288